Never heard
I have actually never heard of this "Black Jack" character before so I wish I was familiar with the manga. This was a pretty dark entry submitted for Valentine's Day. You could have used a background but I guess you don't need that. It's just so new to look at that it's hard for me to judge whether it's good or not. This may be the least of the art pieces you have made, but definitley not bad. I like how his appearance is a mashup of black and white (but really no gray).
I suggest you try putting some more action in your pictures like maybe having him fight. A still frame can be good, but it did not seem that detailed. I suppose his arms are being hid by the blackness of his coat. I like how his blue ribbon tries to give him a more innocent appearance. I think this should please other fans of "Black Jack".